What is the term for a figure of speech that produces an incongruous effect, such as in the phrase "cruel kindness"?

The term that describes a figure of speech which juxtaposes contradictory terms, such as "cruel kindness," is an oxymoron. This rhetorical device blends opposing concepts to create a unique or thought-provoking effect. By combining words with seemingly opposite meanings, an oxymoron highlights the complexity or paradox within a situation, prompting deeper reflection.

For instance, "cruel kindness" suggests that an action intended to be kind also has a harmful component, thus provoking the reader to consider the duality of human emotion and experience. This ability to capture the intricacies of life in concise phrases is what makes oxymorons effective in literature and speech. In contrast, metaphor and simile are figures of speech that involve comparisons, with metaphors asserting that one thing is another, while similes use "like" or "as" to draw parallels. Alliteration, on the other hand, focuses on the repetition of initial consonant sounds in a sequence of words and does not convey the same contradictory meaning found in oxymorons.